Apostol § 315

Brethren, Melchizedek, king of Salem, priest of the Most High God, who met Abraham returning from the slaughter of the kings, and blessed him, to whom also Abraham gave a tenth part of all, first being translated “King of righteousness,” and then also King of Salem, meaning “King of peace,” without father, without mother, without genealogy, having neither beginning of days nor end of life, but made like unto the Son of God, remains a priest for ever. Now consider how great this man was, to whom even the patriarch Abraham gave a tenth of the spoils. And indeed they that are of the sons of Levi, who receive the priesthood, have a commandment to take tithes of the people according to the law, that is, from their brethren, though they have come from the loins of Abraham; but he whose descent is not derived from them received tithes of Abraham, and blessed him that had the promises.